The present invention relates to urethane(meth)acrylates, obtainable by reacting polyether(meth)acrylates, polyester(meth)acrylates or epoxy(meth)acrylates, which have at least one free hydroxyl group and in which from 0.5 to 60 mol % of the (meth)acrylate groups are present in the form of a Michael adduct with primary or secondary amines, with isocyanates, and in particular urethane(meth)acrylates, obtainable by
a) reacting polyether(meth)acrylates, polyester(meth)acrylates and epoxy(meth)acrylates, which may also have at least one free hydroxyl group, with primary or secondary amino compounds which have at least one hydroxyl group, so that from 0.5 to 60 mol % of the (meth)acrylate groups are present in the form of Michael adducts with the amino compounds, and PA1 b) subsequently reacting the product contained in a) with isocyanates.
DE-A-23 46 424 and EP-A-211 978 disclose Michael adducts of primary or secondary amines with acrylates. The amino-modified acrylates described are used, for example, in coating materials and have high reactivity in radiation curing.
EP-A-280 222 describes corresponding Michael adducts of primary monoamines and acrylates. The acrylates mentioned include reaction products of hydroxyl-containing (meth)acrylates with mono- or oligomers containing isocyanate groups.
DE-A-4 007 146 relates to urethane(meth)acrylates containing both amine and, necessarily, urea groups and having a content of amino groups bound by Michael addition. Acrylates which are obtained, for example, by reacting acrylic acid with monohydric or polyhydric alcohols or with the alkoxylated derivatives thereof are mentioned as starting components for the urethane(meth)acrylates.
For the radiation curing, urethane(meth)acrylates having very high reactivity are desirable. Furthermore, the viscosity of the urethane(meth)acrylates should be low so that, for example, when used as coating materials, large amounts of reactive diluents or solvents for establishing the processing viscosity are avoided.